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Exploring earth‐abundant, highly effective, and stable electrocatalysts for overall water and urea electrolysis is urgent and essential for developing hydrogen energy technology. Herein, a simple self‐derivation method is used to fabricate a Fe‐doped Ni3S2 electrode. The electrode exhibits an impressive trifunctional catalyst, with low overpotentials of 290, 198, and 254 mV at 100 mA cm−2 for the oxygen evolution reaction (OER), urea oxidation reaction (UOR), and hydrogen evolution reaction (HER). The durability is higher than 3500 h (146 days) at 100 mA cm−2 for the OER without obvious change. In situ Raman spectra reveal the incorporation of Fe inhibited S dissolution and facilitates the catalyst reconstruction. The density functional theory calculations indicate that the doping of Fe optimizes the adsorption of the rate‐determining step and the d‐band center is closer to the Fermi level, which accelerates the OER process. The two‐electrode electrolyzer needs the cell voltages of only 1.76 and 1.57 V to achieve a current density of 100 mA cm−2 and remarkable durability for more than 500 h at 100 and 500 mA cm−2 for overall water and urea splitting. This work holds great promise for industrial water and urea splitting applications. [ABSTRACT FROM AUTHOR]

Oxygen evolution reaction (OER) is an obstacle to the electrocatalytic water splitting due to its unique four-proton-and-electron-transfer reaction process. Many methods, such as engineering heterostructure and introducing oxygen vacancy, have been used to improve the catalytic performance of electrocatalysts for OER. Herein, the above two kinds of regulation are simultaneously realized in a catalyst by using unique ion irradiation technology. A nanosheet structured NiO/NiFe 2 O 4 heterostructure with rich oxygen vacancies converted from nickel-iron layered double hydroxides by Ar + ions irradiation shows significant enhancement in both OER and hydrogen evolution reaction performance. Density functional theory (DFT) calculations reveal that the construction of NiO/NiFe 2 O 4 can optimize the free energy of O * to OOH * process during OER reaction. The oxygen vacancy-rich NiO/NiFe 2 O 4 nanosheets have an overpotential of 279 mV at 10 mA cm -2 and a low Tafel slope of 42 mV dec -1 . Moreover, this NiO/NiFe 2 O 4 electrode shows an excellent long-term stability at 100 mA cm -2 for 450 h. The synergetic effects between NiO and NiFe 2 O 4 make NiO/NiFe 2 O 4 heterostructure have high conductivity and fast charge transfer, abundant active sites, and high catalytic reactivity, contributing to its excellent performance., (© 2021 Wiley-VCH GmbH.)